Ben Fry posts an amazing visualization of the changes in the six editions of Darwin’s Origin of Species, based on meticulous work done by Dr. John van Wyhe and others. From Ben’s introductory text:

The second edition, for instance, adds a notable “by the Creator” to the closing paragraph, giving greater attribution to a higher power. In another example, the phrase “survival of the fittest” â€” usually considered central to the theory and often attributed to Darwin â€” instead came from British philosopher Herbert Spencer, and didn’t appear until the fifth edition of the text.